Refactor store to accept state as part of params

The old code was returning a fn because TypeScript could not figure out
generic type parameters when params was an object like:

    interface Params<State> {
      a: Reducer<State>
      b: Partial<State>
    }

    function test<State>(params: Params<State>) {
      // ...
    }

packages/client/src/crud/CRUD.test.tsx

@@ -74,7 +74,7 @@ describe('CRUD', () => {
     },
   })
   function getStore() {
-    return test.createStore({reducer})()
+    return test.createStore({reducer})
   }
 
   type Store = ReturnType<typeof getStore>

packages/client/src/test-utils/TestUtils.tsx

@@ -62,12 +62,13 @@ export class TestUtils {
     let store = this.createStore({
       reducer: this.combineReducers(reducers),
       extraMiddleware: [waitMiddleware.handle],
-    })()
+    })
 
-    const withState = (state: DeepPartial<State>) => {
+    const withState = (state: Partial<State>) => {
       store = this.createStore({
         reducer: this.combineReducers(reducers),
-      })(state)
+        state,
+      })
 
       return {withComponent}
     }

packages/jsonrpc/src/redux.test.ts

@@ -143,7 +143,7 @@ describe('createActions', () => {
     })
 
     const reducer = combineReducers({handler, mapping})
-    const store = createStore({reducer})()
+    const store = createStore({reducer})
 
     return {client, store}
   }

packages/redux/src/store/createStore.ts

@@ -1,4 +1,4 @@
-import { Action, applyMiddleware, createStore as create, DeepPartial, Middleware, Reducer } from 'redux'
+import { Action, applyMiddleware, createStore as create, Middleware, Reducer } from 'redux'
 import { PromiseMiddleware, ReduxLogger } from '../middleware'
 
 export interface CreateStoreParams<State, A extends Action> {
@@ -25,9 +25,9 @@ export function createStore<State, A extends Action>(
   if (params.extraMiddleware) {
     middleware.push(...params.extraMiddleware)
   }
-  return (state?: DeepPartial<State>) => create(
+  return create(
     params.reducer,
-    state,
+    params.state,
     applyMiddleware(...middleware),
   )
 }